Soy
58.6% of the world's soybean crop in 2007 was genetically modified (1). GM-soybeans are widely used for cattle, swine, and chicken feeds and are also used to produce food additives. GM-soybeans were first planted in 1996 in the US, possessing a gene that results in herbicide resistance (1). Possible Traits of GM Soybeans The following traits are not contained in all GM soybeans, but are an example of many of the traits that may be present in GM soybeans, depending on the country in which they are produced. Weed Control Herbicide resistant soybeans are very common, especially in North and South America, and contain resistance against herbicides containing glyphosphate as an active ingredient (1). These strains are referred to as "RoundupReady-soya beans" and make up 60% of the world's soybean production. Pathogen Resistance Fungal Resistance: introduced via the transfer of bacterial genes encoding anti-fungal enzymes, like glucanase or chitinase, or by transferring genes encoding funal resistance from other plants. Nematode Resistance: requires extensive crop rotation with nematode-resistant intercropping. Pest Resistance Resistance against butterfly and moth larvae and aphids. Adaptation to extreme climate factors Introduction of genes associated with tolerance to drought or high salt environments Quality Traits -Increased oleic acid content: 86% compared to 23% in natural soybeans, associated with decreased linoleic acid content (1). This decrease in linoleic acid causes lower levels of trans fats. -Modified amino acid content: a common example in soybeans is increased levels of methionine, which is normally found at low levels. Methionine is important if animals such as cattle or swine are fed on only soy meal. -Reduced production of the polysaccharide stachyose, which cannot be digested by most domestic animals or humans, and it has been shown that lower stachylose content results in enhanced growth in pigs and poultry (1). Reduced Raffinosaccharide and Phytic Acid Levels Phytic acid is the most abundant form of phosphate in plant seeds, accounting for about 60% of the total seed phosphate (2). Raffinose and stachyose are also present in most plant seeds, and play a role in protection from damage during dessication, i.e. dessication tolerance. However, multiple studies have shown that phytic acid, raffinose, and stachyose are not critical in plant survival (3); a valuable piece of information for soybean cultivation, because these compounds are "anti-nutritional" in animals fed with high levels of grains and are poorly digested by monogastric animals (2). Mutant soybean lines with decreased expression of raffinosaccharides and phytic acid have been shown to have increased available phosphate and metabolizable energy. Increased dietary available phosphate was also increased when the low phytic acid soybeans were fed to swine (3). RoundupReady Soybeans "RoundupReady Soybeans", briefly described above, are a glyphosphate-resistant variety of soybeans. This is an appealing genetic modification because glyphosphate kills plants by interfering with the synthesis of amino acids phenylalanine, tyrosine, and tryptophan. These amino acids are extremely important because animals cannot make them, thus they must be obtained through the diet, i.e. by eating plants. These three amino acids are synthesized in plants and microbes by 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS), which is not present in animals. RoundupReady soybeans express a version of EPSPS from the CP4 strain of Agrobacterium tumefaciens. The expression of this version of EPSPS is regulated by a 35s promoter known as E35S, which is enhanced by cauliflower mosaic virus (CaMV), a chloroplast transit peptide (CTP4) ...(wiki). Sources: 1. GMO-Compass: Soybeans http://www.gmo-compass.org/eng/grocery_shopping/crops/19.genetically_modified_soybean.html 2. Perera et.al.(2002). American Society of Plant Physiologists. "Biochemical and Molecular Characterization of a Mutation That Confers a Decreased Raffinosaccharide and Phytic Acid Phenotype on Soybean Seeds" 3. Sebastian et.al. (2002) Federation of Animal Science Societies: "Soybean germnplasm with novel genes for improved digestibility in Soy in Animal Nutrition". 4. http://www.biomedcentral.com/1471-2229/13/84